The chemistry and processes used for manufacturing aliphatic and cycloaliphatic epoxy resins via epoxidation of aliphatic and cycloaliphatic hydroxyl containing materials (e.g., cyclohexanedimethanol [CHDM]) using an epihalohydrin are difficult, if not impossible, to drive to full conversion; and such processes produce significant quantities of undesirable partially epoxidized products, such as, for example, cyclohexanedimethanol monoglycidyl ether (CHDM-MGE) (as much as 2 weight percent [wt %] to 20 wt % of the epoxy resin composition), as well as oligomeric co-products (as much as 25-40 wt % of the epoxy resin composition).
It has been found that the presence of residual undesirable components, such as CHDM-MGE, in the aliphatic and cycloaliphatic epoxy (ACE) resin product such as a diglycidyl ether (DGE) or epoxy resin of cyclohexanedimethanol (CHDM-DGE) product, is deleterious to the acid resistance of coatings prepared therefrom. Chain termination caused by the mono-functionality of the CHDM-MGE may also result in reduction of mechanical properties, glass transition temperature (Tg) and reactivity with curing agents. Heretofore, various methods, such as, for example, fractional vacuum distillation, have been used for the partial removal of CHDM-MGE from CHDM-DGE product; however, such known methods used for removal of CHDM-MGE may also remove excessive CHDM-DGE leading to a resulting ACE resin product with an elevated viscosity and a reduced reactivity with curing agents. Thus, to alleviate the aforementioned deficiencies it would be highly desirable to be able to produce an ACE resin which specifically contains low CHDM-MGE (e.g., less than [<] about 6 wt %) while maintaining a high level of CHDM-DGE (e.g., greater than [>] about 80 wt %) with the balance as oligomers.
Various ACE resin products are known to be produced with processes of the prior art including: (1) high purity DGEs of ACE resins, (2) ACE resins produced using non-Lewis acid catalyzed processes, (3) low monoglycidyl ether (MGE) ACE resins, (4) advanced DGEs of ACE resins (containing residual glycidyl ether functionality), (5) partially or completely hydrolyzed aliphatic or cycloaliphatic DGEs, and (6) mixtures of one or more epoxy resins described in (1)-(5) above.
For example, processes for preparing ACE resin products of (1)-(4) above are disclosed, for example, in WO 2012/044442A1; WO 2012/044443A1; WO 2012/044455A1; WO 2012/044458A1; WO 2012/044490A1; WO 2012/047420A2; WO 2012/050688A2; and WO 2012/050777A1; all of which are incorporated herein by reference.
The known processes described above have several drawbacks which make the processes, and the products produced by such processes, undesirable for an industrial scale process for mass producing large quantities of ACE resins. For instance, the known processes use catalysts, and in some instances solvents, that must be removed from the ACE product before the resin can be used in a subsequent operation. In addition, the known processes for producing (5) above produce large quantities of bis-α-glycol species in the epoxy resin in addition to mono-α-glycol species. Such bis-α-glycol species present in the epoxy resin have no curable epoxide groups, and thus, the bis-α-glycol species may: (1) depress Tg of articles (thermosets) made from the epoxy resin containing such species; (2) migrate to the surface of the thermoset causing softness or tackiness; and/or (3) depress mechanical properties such as modulus.
It is desired to provide aliphatic or cycloaliphatic DGEs or epoxy resins particularly, for example, CHDM-DGE, having significantly enhanced properties, such as a low content of CHDM-MGE and/or a low content of hydrolyzable chloride, compared to the above currently known CHDM-DGE resins.